Microstructure evolution,mechanical properties and tailoring of coefficient of thermal expansion for Cu/Mo/Cu clad sheets fabricated by hot rolling

The law of microstructure evolution and mechanical properties of hot roll bonded Cu/Mo/Cu clad sheets were systematically investigated and the theoretical prediction model of the coefficient of thermal expansion(CTE)of Cu/Mo/Cu clad sheets was established successfully.The results show that the deformation of Cu and Mo layers was gradually coherent with an increase in rolling reduction and temperature and excellent interface bonding was achieved under the condition of a large rolling reduction.The development of the microstructure and texture through the thickness of Cu and Mo layers was inhomogeneous.This phenomenon can be attributed to the friction between the roller and sheet surface and the uncoordinated deformation between Cu and Mo.The tensile strength of the clad sheets increased with increasing rolling reduction and the elongation was gradually decreased.The CTE of Cu/Mo/Cu clad sheets was related to the volume fraction of Mo.The finite element method can simulate the deformation and stress distribution during the thermal expansion process.The simulation result indicates that the terminal face of the clad sheets was sunken inward.

Effect of colouring green stage zirconia on the adhesion of veneering ceramics with different thermal expansion coefficients

This study evaluated the adhesion of zirconia core ceramics with their corresponding veneering ceramics, having different thermal expansion coefficients （TECs）, when zirconia ceramics were coloured at green stage. Zirconia blocks （N=240; 6 mm x 7 mm x 7 mm） were manufactured from two materials namely, ICE Zirconia （Group 1） and Prettau Zirconia （Group 2）. In their green stage, they were randomly divided into two groups. Half of the specimens were coloured with colouring liquid （shade A2）, Three different veneering ceramics with different TEC （ICE Ceramic, GC Initial Zr and IPS e.max Ceram） were fired on both coloured and non-coloured zirconia cores. Specimens of high noble alloys （Esteticor Plus） veneered with ceramic （VM 13） （n= 16） acted as the control group. Core-veneer interface of the specimens were subjected to shear force in the Universal Testing Machine （0.5 mm-min-1）. Neither the zirconia core material （P=0.318） nor colouring （P=0.188） significantly affected the results （three-way analysis of variance, Tukey＇s test）. But the results were significantly affected by the veneering ceramic （P=0.000）. Control group exhibited significantly higher mean bond strength values （45.7__.8） MPa than all other tested groups （（27.1__.4.1）-（39.7__.4.7） and （27.4__.5.6）-（35.9___4.7） MPa with and without colouring, respectively） （P^0.001）. While in zirconia-veneer test groups, predominantly mixed type of failures were observed with the veneering ceramic covering ~ 1/3 of the substrate surface, in the metal-ceramic group, veneering ceramic was left adhered 1/3 of the metal surface. Colouring zirconia did not impair adhesion of veneering ceramic, but veneering ceramic had a significant influence on the core-veneer adhesion. Metal-ceramic adhesion was more reliable than all zirconia-veneer ceramics tested.

氟化钇对粉煤灰基堇青石陶瓷合成及性能的影响

本文以粉煤灰、滑石、氧化铝和氧化镁为原料,加入质量分数为0%、0.5%和1.0%的氟化钇,通过高温烧结制备了粉煤灰基堇青石陶瓷样品,研究了氟化钇掺量对样品的物相组成、显微结构及主要性能的影响。结果表明,氟化钇的引入可降低堇青石的生成温度,提高堇青石的物相转化率,显著改善材料的力学性能,同时对热学性能亦有一定积极影响。当氟化钇添加量为0.5%时,样品的综合性能最优。当烧结温度为1300℃时,XRD未见明显杂质峰,样品的体积密度为2.15 g/cm^(3),开孔孔隙率为7.49%,吸水率为3.49%,压缩强度为252.27 MPa,经5次热震试验后压缩强度仍然高至204.65 MPa,比热容为0.770~0.931 J/(g·℃)(25~150℃),热膨胀系数为2.54×10^(-6)℃^(-1)(100~800℃)。与不含添加剂的样品相比,添加0.5%氟化钇样品的体积密度增加了5.2%,开孔孔隙率降低了58.6%,吸水率降低了60.6%,而压缩强度增加了4.6倍,比热容增强而热膨胀系数降低。在粉煤灰基堇青石陶瓷的烧结过程中,氟化钇的引入可使其在较低的温度下形成液相,提高元素迁移率,促进晶粒发育完全且具有细化晶粒的明显效果。氟化钇作为一种有效的烧结助剂,微量的添加即可显著改善粉煤灰基堇青石陶瓷的综合性能。本工作拓宽了高效烧结助剂选择范围,可为高质量陶瓷材料的高温烧结提供一定参考。

钙长石基涂层增强建筑陶瓷的制备和性能研究

建筑陶瓷强度的提升是实现瓷砖薄型化、轻量化生产的关键因素之一。以方解石、烧滑石、高岭土、石英为主要原料,通过改变涂层原料中锂辉石的添加量,调控涂层的物相组成和热膨胀系数,制备了钙长石为主晶相的预应力涂层增强的建筑陶瓷。同时,研究了涂层厚度、球磨时间、保温时间等工艺参数对建筑瓷砖强化效果的影响。结果表明,当涂层中锂辉石添加量为20 wt.%、涂层厚度为86μm,以及在涂层材料球磨时间3 h、烧成温度1190℃、保温时间30 min的条件下,获得了具有较低热膨胀系数且界面结合良好的预应力涂层,此时涂层与基体的膨胀系数差值为3.17×10^(–6)℃^(–1),陶瓷复合样品的抗折强度达到最大值为99.8 MPa,相较于无涂层的样品(66.3 MPa)强度提高了50.5%。

预制体结构对SiC_(f)/SiC复合材料力学和热性能的影响

本文采用化学气相渗透法制备了具有二维多层、三维角联锁机织和多轴三维编织三种预制体结构的SiC_(f)/SiC复合材料。在综合分析纤维排列、SiC基体和孔隙分布的基础上,详细讨论了预制体结构对SiC_(f)/SiC复合材料力学性能和热性能的影响。结果表明,复合材料的力学性能和热导率受纤维排列方式和复合材料密度的综合影响,而热膨胀系数主要受纤维排列方式的影响。此外,二维多层复合材料、三维角联锁机织复合材料和多轴三维编织复合材料的热导率可以分别用串联模型和平行模型来解释。多轴三维编织复合材料由于内部具有连续的可以作为热流快速通道的三维网状SiC基体层,因此具有较高的室温热导率。而随着温度的升高,SiC声子间的散射逐渐增强,SiC基体层在多轴三维编织复合材料中作为声子传播快速通道的作用逐渐减弱,热导率随温度降低的趋势更明显。

近零膨胀堇青石陶瓷的制备

堇青石陶瓷由于具有热膨胀系数较低、力学性能优良及密度低等优点,是理想的光刻机方镜材料。目前,国内对方镜用堇青石陶瓷研究较少,因此,开展相关研究对于推进高端堇青石陶瓷零部件的国产替代具有重要意义。以La^(3+)为掺杂剂,采用溶胶—凝胶工艺制备了Mg_((2−x))La_(x)Al_(4)Si_(5)O_((18+0.5x))系列堇青石陶瓷,研究了La^(3+)掺杂对堇青石陶瓷显微结构、热膨胀性能及力学性能的影响。结果表明:随着La^(3+)引入量的增加,堇青石陶瓷样品的热膨胀系数从负膨胀逐渐向正膨胀转变。当La^(3+)引入量(x)为0.15时,所得样品在(22.0±0.5)℃的热膨胀系数绝对值≤0.020×10^(−6)K^(−1),此时样品的弯曲强度为211.44 MPa,弹性模量为145.77 GPa,达到了方镜材料的性能指标要求。在烧结过程中,引入的La^(3+)会取代堇青石结构中的Mg^(2+)造成六元环的畸变,另外还会生成液相促进致密化烧结,这两方面的协同作用实现了对堇青石陶瓷性能的有效调控。

不同针刺工艺对C/C复合材料性能影响

通过改变刺针直径、针刺密度和预制体密度等调控针刺工艺来制备C/C复合材料,对比相同沉积工艺下,预制体结构对C/C复合材料密度及沉积速率的影响,以及不同针刺工艺对C/C复合材料弯曲性能,拉伸性能,压缩性能及热学性能影响。结果表明:采用刺针直径为0.7 mm,针刺密度为26~31针/cm^(2),预制体密度为0.33~0.37 g/cm^(3)制备的C1试样,CVI沉积后平均增密最大为1.0 g/cm^(3),平均增密速率最大为2.86 g/cm^(3).s,且C1试样整体力学性能最佳,较常规工艺制备的C/C复合材料来说,抗弯强度提高31%,抗拉伸强度提高22.3%,压缩最大载荷提高37%。

Effect of Si content on microstructure and properties of Si/Al composites

Si/Al composites with different Si contents for electronic packaging were prepared by spark plasma sintering （SPS） technique. Properties of the composites were investigated, including density, thermal conductivity, coefficient of thermal expansion and flexural strength. The effects of the Si content on microstructure and thermal and mechanical properties of the composites were studied. The results show that the Si/Al composites consist of Si and Al components and Al uniformly distributes among Si grains. The relative density of the Si/Al composites gradually increases with the decrease of Si content and reaches 98.0% when the Si content is 50%. The thermal conductivity, the coefficient of thermal expansion and the flexural strength of the composite all decrease with the increase of the Si content, and an optimal matching of them is obtained when the Si content is 60%（volume fraction）.

Preparation and Performance of Al_2TiO_5-TiO_2-SiO_2 Honeycomb Ceramics by Doping Rare Earth

A preferable honeycomb ceramics of Al2TiO5-TiO2-SiO2 doped by CeO2 and Er2O3 with high performance was prepared by means of extrusion molding and the effects of CeO2 and Er2O3 on the mechanical strength, thermal stability, and sintering temperature of ATS ceramics were mainly investigated. The experimental results and the microscopic analysis by scanning electron microscope, X-ray powder diffxaction, and TG-DSC showed that adding CeO2 and Er2O3 into ATS could prohibit the growth of their crystal grains and make their size uniform, which finally decrease its sintering temperature, and also enhance its mechanical performance as well as thermal stability. After the reforming, ATS doped by 0.5% CeO2 ＋0.5% Er2O3 was sintered at 1250 ℃, its bending strength reached to 177A MPa and thermal expansion coefficient was 3.8 ~ 10^-6/℃ at 25 - 1000℃, which provided a promising basis of making monolithic honeycomb catalyst of deNOx.

Effect of ZrO_2 Content on the Properties of Diamond Grinding Wheel Vitrified Bond

The effect of ZrO2 content on the performance of vitrified bond was discussed. The results showed that when the ZrO2 content was less than 2 mol%, Zr4＋ could enter into the glassy network as mending nets and agglomeration composition. In this case, with the increasing of ZrO2, the vitrified bond＇s bending strength increased and the expansion coefficient decreased. It was also found that the wetting angle between the vitrified bond and diamond got small because Zr4＋ was enriched on diamond surface. When ZrO2 content was more than 2 mol%, a part of ZrO2 existing in vitrified bond as ZrO2 particles played the role in nucleating agents and promoting the separation of spodttrnene. When ZrO2 content was 3 mol%, the bending strength of the vitrified bond reached its maximum of 128 MPa and the wetting angle with the diamond reached its minimum of 37.6°.

Effect of cenospheres addition on microstructure and properties of AZ91D alloy

The cenospheres/AZ91D composites were fabricated by melt stir method. The phases, microstructure and tensile fracture morphology of the composites were analyzed using XRD, Olympus metallurgical microscopy and SEM methods. The thermal expansion coefficient(CTE) and tensile properties were measured. The results showed that the cenospheres distribute uniformly in the Mg alloy matrix and refine the matrix microstructure. Mg2 Si and MgO were found in addition to α-Mg and β-Mg17Al12 phases using XRD. The CTE of the composites reduced after the cenospheres are added. The yield strength of the composites increases significantly with an increase in the mass fraction and a decrease in the size of the cenospheres. The tensile strength of the composites achieves maximum when the mass fraction of cenospheres is 9wt.% and the size of cenospheres is 80 μm. The fracture mechanism of the composites is cleavage fracture.

喷射成形(SiC_(p)+β-LiAlSiO_(4))/6092Al基复合材料的界面结构及性能

采用喷射成形技术和模锻工艺成功制备45%SiC_(p)/6092Al、5%β-LiAlSiO_(4)/6092Al和(45%SiC_(p)+5%β-LiAlSiO_(4)(Euc))/6092Al(质量分数)基复合材料。利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)和X射线衍射仪(XRD)对复合材料试样的显微组织、界面结构及物相成分进行分析,采用热膨胀仪和电子万能试验机分别对复合材料试样的热膨胀性能、弯曲强度和模量进行测试。结果表明:(45%SiC_(p)+5%Euc)/6092Al基复合材料中碳化硅颗粒和Euc颗粒在6092Al基体中分布均匀,并与铝基体形成强力结合界面,SiC_(p)/Al和Euc/Al界面平直清晰,没有发现界面反应。复合材料试样经固溶人工时效后,在303~473 K温度范围内,(45%SiC_(p)+5%Euc)/6092Al基复合材料试样的线膨胀系数为14.68×10^(−6)K^(-1),弯曲强度和模量分别达到589 MPa和165 GPa。

低热零点漂移的高温绝压压力传感器

传统的高温绝压压力传感器一般采用硅和玻璃进行阳极键合来制备绝压腔。由于高温环境下硅片和硼硅玻璃的热膨胀系数不匹配,从而产生较高的热零点漂移。文中提出了一种低热零点漂移的压力传感器设计方案,由硅-玻璃-硅的三层结构代替普通的双层阳极键合结构,并给出了热力学仿真模型。分析表明:改变传感器硅与玻璃的结构比例,实现应力匹配可以有效减小热应力。对芯片进行了高温实验测试,发现传感器的热零点漂移变化率减小了50%。

石墨烯对铁基金属结合剂金刚石磨具性能的影响

本文通过调整Fe-Co-Cu-Sn中石墨烯的含量来探究石墨烯对铁基金属结合剂金刚石磨具性能的影响。通过X射线衍射仪、扫描电子显微镜、万能力学试验机等测试了铁基金属结合剂金刚石磨具的显微结构、物相结构、力学性能和物理性能。结果表明:结合剂中石墨烯的含量仅对晶相含量有影响;当石墨烯含量为0.4%(质量分数)时,磨具的抗弯强度最高,为256.0 MPa,较无石墨烯磨具提高了17.4%;随着石墨烯含量增加,石墨烯由片状均匀分布转变为逐渐团聚,断口组织由脆性断裂转变为韧性断裂,磨具的热膨胀系数逐渐降低,导热系数逐渐提高;磨具的磨耗比呈先增加后减少的趋势,当石墨烯含量为0.4%时,磨耗比最高,为199.8,较不添加石墨烯的磨具提高了约21%。

温度对柴油机缸盖用HT325力学性能的影响

随着国家排放要求不断提高,实现碳中和,发动机厂不断研究提升满足耐高温、高爆压、高性能、高功率柴油发动机缸盖材料,以便达到耐高温高压的稳定性能要求。本文以灰口铸铁HT325为研究对象,通过变温拉伸和压缩实验并结合化学成分和金相组织分析,研究了温度对HT325铸件力学性能的影响规律。在25℃~450℃温度范围设立10个温度点,保温30 min.研究结果表明:1)HT325材料的热膨胀系数随温度的升高而单调增加;2)HT325弹性模量随温度的升高而单调呈下降趋势;3)HT325材料拉伸应力应变曲线表现出明显的非单调变化;4)HT325的抗拉强度整体上随温度的升高而降低,但在250℃和350℃附近出现反常的回升现象;5)HT325的抗压强度在200℃~300℃温度区间内无明显波动,这将具有广阔的应用前景;6)温度对灰口铸铁HT325抗拉和抗压强度的影响有显著差异。本研究结果为优化气缸盖材料性能、改良铸造工艺、提高产品安全性和节约成本提供了理论与试验依据。

锶氟共掺杂羟基磷灰石的热物性和抗折强度研究

采用化学沉淀法制备了锶氟共掺杂羟基磷灰石(Sr FHA),通过X射线衍射(XRD)、高温膨胀仪、扫描电镜(SEM)和电子万能试验机研究了Sr、F掺杂对HA高温热稳定性、高温烧结性能、热膨胀系数和抗折强度的影响。结果表明,Sr掺杂使HA的热稳定性降低,F掺杂则相反。适量的Sr掺杂有利于HA的烧结致密化,当锶掺杂量为5%时,HA具有最大的抗折强度(35.86 MPa)和最大的热膨胀系数(11.86×10^(-6),600℃)。F掺杂能降低磷灰石热膨胀系数(CTE)和提高抗折强度,但抑制烧结。

高抗冲击性金刚石复合煤截齿的研究

如今煤矿行业对开采设备的要求愈发严苛,为满足其耐磨、高效、长寿命的工业化生产需求,研制出了一种高抗冲击性能金刚石复合煤截齿。该截齿由硬质合金基体和金刚石聚晶层组成,整体外观类似于子弹状,齿头部轮廓为圆滑球面,齿腹部为凸出的圆弧面,且两部分平滑过渡对接。通过加入过渡聚晶层设计,改变硬质合金界面处金刚石粒度,将各层之间的结合面设计成多段圆弧曲线,有效解决煤截齿金刚石聚晶层在工作冲击状态下的易破碎脱落问题。

低热膨胀系数复合水泥的研究

水泥基材料的高脆性及高热膨胀系数导致水泥基制品在受热时易产生膨胀开裂。本文研究不同混合材对复合水泥热膨胀系数及强度的影响,探究低热膨胀系数复合水泥的制备方法。结果表明,采用矿粉和堇青石作为混合材可以显著降低复合水泥的热膨胀系数,当矿粉与堇青石的相对含量为1:1时,复合水泥具有较高的抗折和抗压强度。在保证复合水泥强度的前提下,复合水泥的热膨胀系数可以降低至5.2×10^(-6)/℃,较P·Ⅱ52.5水泥降低50%以上。

复合材料补片胶接修补研究进展

介绍了复合材料补片胶接修补的优越性及关键技术。详细论述了复合材料补片胶接修补的设计分析以及修补的无损检测和试验验证。追踪报道了补片胶接修补的研究方法。

温度对HMX基PBX炸药热膨胀系数和热导率的影响

用热膨胀仪和闪光导热仪研究了温度对HMX基PBX的热膨胀系数和热导率的影响。结果表明,在低于330K时,HMX基PBX的线膨胀系数约为5.34×10-5 K-1;在330～350K,线膨胀系数迅速增大到13.47×10-5K-1,随着黏结剂软化,线膨胀系数随之减小到8.04×10-5 K-1。在293～373K,HMX基PBX的比热容从0.978J.g-1.K-1线性增长到1.254J.g-1.K-1,但在343K附近黏结剂融化存在异常偏大值;HMX基PBX的热扩散率从0.256mm2.s-1下降至0.179mm2.s-1,通过比热和热扩散率实验数据计算获得的热导率从0.462W.m-1.K-1下降至0.406W.m-1.K-1。基于分子晶体传热理论模型建立了比热和导热系数的温度关系函数,HMX基PBX的导热机制符合两相串联模型。